By the way I spent about a half-hour searching for Bungie's ticker symbol and it simply does not exist.
Companies don't have to have a ticker to have shareholders. Only publicly-traded companies will have tickers, but all companies have shareholders (even if it's just one owner that has all the shares). A publicly-traded game developer would be an extraordinarily rare thing. But one with a number of shareholders is quite common. Usually when starting up a development house it's common for whomever is starting it up to offer the lead positions a share in the new company to lure them away from whatever sure thing they've got going on elsewhere.
So you've got the lead programmers, producers, etc that all initially started up this new company BECAUSE they wanted to make something different on their own that, now, for the past few years have been on somewhat of a tight leash creatively I'm sure; though as the head people at Bungie they've undoubtedly been very nicely compensated for it. So they can run off and repeat the same process, which is what developers do, and why for every big success you'll see a half-dozen new development houses pop up as the shareholders take their cuts of the profits and run. Or, if you like the people you work with, you take the profits "The Man" has been paying you and you offer to buy yourself back out again.
And then Microsoft, faced with either a mass exodus from Bungie, has to decide to take the offer which will at least give you future rights of first refusal on Bungie games, or face having Bungie gutted from the inside as all the employees leave which could make it a virtually worthless asset anyhow.